Realization Methodology of a 5-axis Spline Interpolator in an Open CNC System

By making use of the advantages of non-uniform rational B-spline （NURBS） curves to represent spatial curves, an instruction format with double NURBS curves suitable for 5-axis coordinated real-time interpolation is presented to replace the current 5-axis coordinated linear interpolation method defective in low-speed, low-accuracy and enormous numerical control （NC） files in sculptured surface machining. A generation procedure of the NC files with the presented format is introduced and the method to realize the interpolation in an open computer numerical control （CNC） system is developed by ourselves. These illustrated the feasibility of the proposed method and its capability of avoiding all the shortages of 5-axis linear interpolation method.

CNC SYSTEM OF FLEXIBLE FIXTURE IN AIRCRAFT COMPONENT MANUFACTURING AND ASSEMBLY

The computer numerical control（CNC） system is suited to control varied types of flexible fixtures in aircraft component manufacturing and assembly. The mechanisms and control requirements of flexible fixtures are presented and analyzed. The hardware and software architecture and implementation of CNC system are pro- posed. The flexible fixture mechanism is described using configuration parameters. According to the parameters, the CNC system automatically generates the control feature and the human machine interface （HMI） operation function. The CNC system is implemented in a flexible fixture for skin-strlnger assembly, and results show the effectiveness of the system.

Key Technology of Embedded System Implementation for Software-based CNC System

The software-based computer numerical control（CNC） system includes three types of tasks： periodic real-time tasks, aperiodic real-time tasks, and non-real-time tasks. The tasks are characterized by concurrency, hybridization, and correlation, which make system implementation difficult. The conventional scheduling algorithm can not meet the demands of system implementation in the software-based CNC system completely. The uncertainty factors when running real-time tasks affect control performance by degrading manufacturing accuracy as a result of system resource and processor use restrictions. To address the technical difficulty of embedded system implementation, a novel fuzzy feedback scheduling algorithm based on output jitter of key real-time tasks for a software-based CNC system is proposed. Time characteristics, such as sampling jitter, input-output jitter, and non-schedulability are discussed, followed by quantification through simulations of the impact of time characteristics on manufacturing accuracy. On the basis of this research, the scheduler architecture is designed, and then the algorithm table is calculated. When the system resource changes, the key periodic real-time tasks meet their deadlines by means of dynamically adjusting the task period. The simulated results show that the machining precision rises by an order of magnitude for the proposed scheduler in resource-constrained software-based CNC systems. Moreover, unlike conventional feedback scheduling methods, the algorithm in this paper does not rely on the availability of task execution times and is easy to implement while incurring only a small overhead.

Real-time Synchronization Method Based on Dual Ring Fieldbus in CNC System

As the popularization of dual ring fieldbus, the optimized dual ring synchronization methods are still in short. The current synchronization methods are generally established in traditional industrial fieldbus, in which transmission is commonly considered in single track, the two-way transmitting cannot take full effect, and would result in unwanted idle load on equipment lines. In stamp-transferring part, the synchronizing algorithm is not properly processed to diminish the latency, so the real-time performance of entire system cannot be ensured. To support the synchronization control of stations in the CNC system, a real-time time synchronization method for dual ring fieldbus in the CNC system is designed in this paper. In this method a synchronizing message transmission scheme based on dual ring architecture and the synchronization algorithm between master and secondary stations are integrated. In the scheme, the clock models of both master and secondary stations are optimized with corresponding modules and the stamp data transmission based on the dual ring fieldbus is devised exclusively, so the transmitting efficiency improves with less idle work. In the algorithm, all the secondary stations can accomplish the consistent state with master station by updating clock discrepancy information in one communication cycle, and it takes the advantage of two-way transmitting and makes the best use of dual ring structure, so the real-time performance of the system can be promoted while retaining the precision of synchronization. To evaluate the performance, the costs of the method and errors during synchronizing are noted and analyzed based on the actual running environment in the industrial fieldbus. The results show that it reduces communication cost and ensures the smoothness of the system with low lag effects under heavy load. The proposed time synchronization method optimizes the architecture of sync message transmission in dual ring fieldbus, and improves the efficiency of time synchronization in the stations of CNC system.

Time between failures model and failure analysis of CNC system

To provide basis for the reliability improvement design of CNC system, the failure data of a type of CNC system in one year are collected under field conditions in workshops. The distribution model parameters of time between failures are estimated by least square method and hypothesis testing is done by d-test method. It is proved that the time between failures of the CNC system follows Weibull distribution and the system has entered into the wear-out failure period. The failure positions and failure causes are analyzed further to indicate the weak subsystems of the CNC system. It can be found that servo unit, electrical system, detecting unit and power supply are principal failure positions and the main failure cause is breakage of components. The corresponding improvement measures are put forward. The paper provides a reference to reliability design and analysis of CNC system for the manufacturer and has great guidance to using and maintaining CNC system for the user.

OPEN ARCHITECTURE CNC SYSTEM HITCNC AND KEY TECHNOLOGY

Aiming at the characteristics of modularity and reconfigurable in open architecture computer numerical control （CNC） system, the open architecture CNC system, Harbin Institute of Tech- nology computer numerical control （HITCNC）, is researched and manufactured based on the interface standards. The system＇s external interfaces are coincident with the corresponding international standards, and the internal interfaces follow the open modular architecture controller （OMAC） agreement. In the research and manufacturing process, object-oriented technology is used to ensure the openness of the HITCNC, and static programming is applied in the CNC system according to the idea of modularization disassembly. The HITCNC also actualizes real-time and unreal-time modules adopting real-time dynamical linked library （RTDLL） and component object model （COM）. Finite state ma- chine （FSM） is adopted to do dynamically modeling of HITCNC. The complete separation between the software and the hardware is achieved in the HITCNC by applying the SoftSERCANS technique. The application of the above key techniques decreases the programming workload greatly, and uses software programs replacing hardware functions, which offers plenty technique ensures for the openness of HITCNC. Finally, based on the HITCNC, a three-dimensional milling system is established. On the system, series experiments are done to validate the expandability and interchangeability of HITCNC. The results of the experiments show that the established open architecture CNC system HITCNC is correct and feasible, and has good openness.

Cam Profile Grinding CNC System Based on Open Architecture

This paper studies some key technologies of CNC system for cam grinding. The mathematical motion model for cam grinding is established according to the harmony of reciprocating motion of the grinding wheel and the rotating motion of the workpiece. The method of using the linear servomotor to accomplish the grinding wheel tracking is developed and the dynamic model of the system is analyzed. Then the cross-coupled biaxial error compensation model is proposed. Finally, the hardware and software of the control system are designed based on open architecture. Some algorithms , such as spline fitting and interpolation for cam contour, velocity control and feed control, are presented to improve grinding precision.

Development of an E-maintenance System for a CNC System

Globalization and rapid growth of network technologies have changed the traditional patterns of device maintenance. E-maintenance has emerged and is widely used in many manufacturing systems. In this paper, a new architecture of an E-maintenance system is proposed, which consists of E-maintenance centre, embedded CNC gateway and CNC terminal. The E-maintenance centre provides the technical support and service for customers based on Internet and communication technologies. The embedded CNC gateway serves as an agent between the public and plant device network, and provides web-based access for the CNC system. A reconfigurable CNC terminal is highly desired in a signal measuring and analysing system, which is built on the top of component and software bus based models. Finally, the E-maintenance system for the CNC machine is implemented and the experiments show that the architecture of an E-maintenance system can effectively reduce the downtime of devices, the responding time of maintenance work, and increase both the quality and the productivity of enterprises.

ANOTHER KEY BREAKTHROUGH IN CHINESE DEVELOPMENT OF HIGH-END CNC SYSTEMS

Next to the successful development of the SS-8510 High-end CNC System in 1993, another feat was one year later achieved in development of the SS-8520/8530 CNC Systems,all being accomplished by the Shenyang Institute of Computational Technology,an affiliate to the CAS in Northeast China.Recently,the new models have passed a technical appraisal hosted by the CAS. Modem manufacture is the industrial basis for a country’s economic growth and the national defense.Its technological level plays a pivotal role in

Circular Interpolation Algorithms of 5-Axis Simultaneous CNC System

Spatial circular arc can be machined conveniently by a 5-axis NC machine tool.Based on the data sampling method,circular interpolation in two-dimensional plane is discussed briefly.The key is to solve the problem of circular center ex- pressed in the workpiece coordinate system by means of the transformation matrix.Circular interpolation in three-dimensional space is analyzed in detail.The method of undetermined coefficient is used to solve the center of the spatial circle and the method of coor- dinate transformation is used to transform the spatial circle into the XY-plane.Circular arc in three-dimensional space can be ma- chined by the positional 5-axis machining and the conical surface can be machined by the continuous 5-axis machining.The velocity control is presented to avoid the feedrate fluctuation.The interpolation algorithms are tested by a simulation example and the inter- polation algorithms are proved feasible.The algorithms are applied to the 5-axis CNC system software.

Investigation on full distribution CNC system based on SERCOS bus

A full distribution CNC system based on SERCOS bus is studied in accordance with the limitations of traditional PC-based motion card. The conventional PC-based motion control card is dispersed into several autonomous intelligent servo-control units with the function of servo driver. The autonomous intelligent servocontrol units realize the loop control of position, velocity and current. Interpolation computation is completed in PC and the computational results are transferred to every autonomous intelligent servo-control unit by high speed SERCOS bus. Software or hardware synchronization technology is used to ensure all servomotors are successive and synchronously running. The communication and synchronization technology of SERCOS are also researched and the autonomous intelligent servo-control card is developed byself. Finally, the experiment of circle contour process on a prototype system proves the feasibility.

Development and Application of the NT Device Driver in CNC System

The key technology of open architecture CNC systems kernel device driver,including the interrupt mechanism, I/O subsystem, the structure of device driver and the communication between the driver and the application program, is discussed in the paper and a specific application is given at the end.

Study on Behavior Model in Open Architecture CNC System

Since a CNC controller has different real-time require-ments in difference levels,proper methods for dynamicmodeling must be employed when a CNC controller isdesigned.Based on behavior model in this paper,a newdynamic modeling method is given and used to analyzethe life cycle of application objects and their interactionsin an open architecture CNC controller modeling.Be-sides,the paper develop a solution how to realize recon-figurable structures in CNC systems and seamless con-nection between fuuction modules and system.

Optimum Selecting Method of CNC System′s Accessories

The object of this dissertation is to select the best-quality product in CNC system′s accessories.It applies the relative theories of Fuzzy Mathematics to solve the issue,and it sets up the effective optimum selecting theory model.Moreover,it presents a kind of applicable way,which selects the best-quality product,and proves its availability by the living case.

WORKPIECE LOCATING AND POST PROCESSING SYSTEMS ON 6-DOF CNC MILLING MACHINE

A conventional non-computerized numerical control （CNC） machine is updated by mounting a six degree-of-free （DOF） parallel mechanism on it, thus obtaining a new CNC one. The structure of this CNC milling machine is introduced, and the workpiece locating system and the post processing system of the cutter location （CL） data file are analyzed. The new machine has advantages of low costs, simple structure, good rigidity, and high precision. It is easy to be transformed and used to process the workpiece with a complex surface.

A low glitch 12-bit current-steering CMOS DAC for CNC systems

A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC （computer number control） systems is presented. To reduce the glitch and increase the SFDR （spurious-free dynamic range）, a low crosspoint switch driver and a special dummy switch are applied. In addition, a 4-5-3 segmental structure is used to optimize the performance and layout area. After improvement, the biggest glitch energy decreased from 6.7 pVs to 1.7 pVs, the INL decreased from 2 LSB to 0.8 LSB, the SFDR is 78 dB at a 100-MSPS clock rate and 1 MHz output frequency. This DAC can deliver up to 20.8 mA full-scale current into a 50 Ω load. The power when operating at full-scale current is 163 mW. The layout area is 1.8 × 1.8 mm2 in a standard 0.35-um CMOS technology.

Research on CNC Turning System of Aspheric Machining Grinding Wheel

The technology of machining aspheric surface with high precision is the premise for the application of aspheric surface. The grinding machining with error compensation is a commonly used method to machine aspheric surface, which will directly influence the quality of aspheric workpiece surface. Multifunctional CNC grinding wheel truing system is a four-axis CNC truing system which can be applied to grinding wheel truing. In this system, DSP-based multi-axes motion control card is adopted as the controller, and visual C++ is used as development tool. When the design of hardware and software is completed, the system can implement truing of various grinding wheel with high precision aspheric machining such as plane grinding wheel, arc grinding one, and sphere grinding one.

基于CNC系统的数控车床故障诊断方法

数控车床在现代制造业中扮演着重要角色,其故障诊断对于保障生产效率至关重要。提出一种基于计算机数控(Computer Numerical Control,CNC)系统的数控车床故障诊断方法,通过运行参数采集、数据预处理、特征提取和支持向量机算法,实现故障模式的智能识别。实验结果表明,该方法在故障检出率、误报率、诊断时间和准确率等方面均优于传统方法,为数控车床的智能化维护提供了新的思路,有助于提高设备的可靠性和生产效率。

Modeling Method for Flexible Energy Behaviors in CNC Machining Systems

CNC machining systems are inevitably confronted with frequent changes in energy behaviors because they are widely used to perform various machining tasks. It is a challenge to understand and analyze the flexible energy behaviors in CNC machining systems. A method to model flexible energy behaviors in CNC machining systems based on hierarchical objected-oriented Petri net(HOONet) is proposed. The structure of the HOONet is constructed of a high-level model and detail models. The former is used to model operational states for CNC machining systems, and the latter is used to analyze the component models for operational states. The machining parameters having great impacts on energy behaviors in CNC machining systems are declared with the data dictionary in HOONet models. A case study based on a CNC lathe is presented to demonstrate the proposed modeling method. The results show that it is effective for modeling flexible energy behaviors and providing a fine-grained description to quantitatively analyze the energy consumption of CNC machining systems.

Design and implementation of five-axis transformation function in CNC system

To implement five-axis functions in CNC system, based on domestic system Lan Tian series, an improved design method for the system software structure is proposed in this paper. The numerical control kernel of CNC system is divided into the task layer and the motion layer. A five-axis transformation unit is integrated into the motion layer. After classifying five-axis machines into different types and analyzing their geometry information, the five-axis kinematic library is designed according to the abstract factory pattern. Furthermore, by taking CA spindle- tilting machine as an example, the forward and the inverse kinematic transformations are deduced. Based on the new software architecture and the five-axis kinematic library, algorithms of RTCP （rotation tool center point control） and 3D radius compensation for end-milling are designed and realized. The milling results show that, with five-axis functions based on such software struc- ture, the instructions with respect to the cutter＇s position and orientation can be directly carried out in the CNC system.